The invention relates to methods of forming cervical caps.
Cervical caps, i.e., cap-shaped devices which fit over a patient's cervix to prevent ingress of sperm into the patient's uterus, have long been used for contraception. Most of these devices are not custom molded to the shape of the individual patient's cervix, but are merely provided in several sizes. While many of these non-customized devices provide good contraception, they cannot be left in for extended periods of time, and typically must be removed after as little as 48 hours, making them hardly more convenient than diaphragm-type contraceptive devices.
Other cervical caps have been custom molded by a three-step process, typically requiring two visits to the clinician before the cap can be completed. This process involves the forming of a casting of the patient's cervix, typically using an alginate or polysiloxane impression material, making a plaster or stone model of the cervix using the casting, and thermoforming of a thermoplastic, e.g., a styrene-butadiene block copolymer, over the model. Custom forming of the cap allows the cap to conform very closely to the cervix, preventing buildup of fluids and reducing the possibility of infection, thus allowing the patient to keep the cap in place for much longer periods of time. For the cap to be left in continuously in place for extended periods however, it is necessary to provide a one-way valve in the cap to allow egress of fluids from the uterus, while preventing any ingress of sperm. The design of some of these valves has reduced the contraceptive effectiveness of the cap.
Another method of forming a cervical cap in situ is disclosed in U.S. Pat. No. 4,007,249. According to this method, a layer of curable elastomeric material is applied directly to the surface of the patient's cervix and allowed to cure in place.
U.S. Pat. No. 5,123,424 proposes yet another method for forming a cervical cap in situ. In this method, a cervical cap, which includes a rim and a dome, is fitted to the patient's cervix, such that a gap is formed between the dome and cervix, and a biocompatible material is injected into the gap while the cap is in place. The finished cervical cap includes the cervical cap which was fitted to the patient and the biocompatible material, which bonds to the inner surface of the dome.